How to improve the abrasion resistance and adhesion of UV varnish for Black Glossy Chocolate Boxes?

How to improve the abrasion resistance and adhesion of UV varnish for Black Glossy Chocolate Boxes?

UV glazing is a common surface finishing process in the packaging and printing industry. Color box printing enterprises (especially those with export business in Japan, Europe and the United States and other countries and regions) often encounter such problems: after UV varnish for Black Glossy Chocolate Boxesing the printed product, the wear resistance of the UV varnish for Black Glossy Chocolate Boxes film layer and the Poor adhesion, especially when the print is printed with metallic ink (gold or silver) and then UV varnish for Black Glossy Chocolate Boxesed.

Under normal circumstances, color box printing companies often solve this problem by replacing UV varnish for Black Glossy Chocolate Boxes. In fact, we should not only limit our thinking to replacing UV varnish for Black Glossy Chocolate Boxes, but should diverge our thinking and convert our thinking to changing the production process route of color boxes or adjusting relevant process parameters.

  Solutions

The conventional production process route of corrugated color box is: plate making and paper cutting→normal printing→UV primer→UV surface oil→corrugated mounting→die cutting→gluing box. After many tests, the author summarizes the methods for improving the production process of corrugated boxes as follows.

(1) Plate making and paper cutting → UV ink printing + online UV varnish for Black Glossy Chocolate Boxesing. Tests have shown that this production process can greatly improve the abrasion resistance and adhesion of UV varnish for Black Glossy Chocolate Boxes on metal UV inks, but metal UV inks are relatively rare in the market, require special customization, are expensive, and must be printed with UV printing press. In general, most of the small color box printing enterprises do not have UV printing machines, so this production process is only suitable for some color box printing enterprises, and the general promotion is of little significance.

(2) Plate making and paper cutting → ordinary printing → screen printing UV varnish for Black Glossy Chocolate Boxesing. This production process can also solve the problems of poor wear resistance and adhesion of UV varnish for Black Glossy Chocolate Boxes on metal inks, but the cost of screen printing UV varnish for Black Glossy Chocolate Boxes is higher, and the environmental protection performance is not as good as that of water-based UV varnish for Black Glossy Chocolate Boxes. In addition, many color box printing enterprises do not have automatic screen printing machines, but only semi-automatic screen printing machines with low production efficiency. Therefore, this production process can only be applied to some color box printing enterprises, and is not worthy of general promotion.

Finally, after repeated verifications, we have clarified the idea of to solve this problem: use high wear resistance UV surface oil to improve wear resistance, and ensure the adhesion of UV primer by adjusting process parameters or changing materials. Due to two varnishes, the varnish film layer is thicker, which makes the abrasion resistance of the high-abrasion-resistant UV topcoat more secure. The next step only needs to focus on solving the key factors affecting the adhesion of UV varnish for Black Glossy Chocolate Boxes-printing ink and UV primer.

  solution

Before solving the problem, you first need to understand the customer's requirements and testing methods for color boxes.

(1) To test the wear resistance of UV varnish for Black Glossy Chocolate Boxes on color boxes, the methods are as follows: ① If the color boxes need to be shipped by sea, a box of actual products can be packed in the cardboard box used in the actual customs declaration, or a box with the same weight and specifications as the actual products can be packed. The product model is placed on a simulated transportation test machine (vibration test bench) and vibrated for more than 2 hours. It is qualified if there is no obvious UV varnish for Black Glossy Chocolate Boxes film or ink layer on the surface of the color box; ② Put the color box sample on the friction tester On, use a 22N weight to wipe back and forth 80 times (the weight and times can be determined according to the customer's requirements), if there is no obvious UV varnish for Black Glossy Chocolate Boxes or ink drop, it is qualified.

(2) Detect the adhesion of the UV varnish for Black Glossy Chocolate Boxes on the color box, the method is as follows: ①Affix the 3M transparent tape firmly on the surface of the color box, and then tear off the tape rapidly and forcefully at a 45-degree angle to prevent the UV varnish for Black Glossy Chocolate Boxes film from sticking. The layer or ink layer is qualified; ②Use HB pencil lead to scribble back and forth on the surface of the UV varnish for Black Glossy Chocolate Boxes film layer of the color box, and it is qualified if the UV varnish for Black Glossy Chocolate Boxes layer or ink layer is not scratched.

There are two main structures of silver powder contained in silver ink currently on the market: one is a granular structure close to a circle; the other is a flaky structure similar to "fish scales". The former is more conducive to the adsorption of UV primer, and the latter can better show the metallic luster and texture of the ink. However, there is only one structure of gold powder contained in the gold ink currently on the market: a flaky structure similar to "fish scales". Therefore, the adhesion of UV primer on gold ink is much worse than that on silver ink, and it is more troublesome to solve. The author also learned that the adhesion of oil-based UV primers on metal inks is better than that of water-based UV primers. However, oil-based UV primers are also used in the improved process, but their adhesion problem on metallic inks has not been resolved, so we have to shift our focus to the improvement of metallic inks.

When testing the adhesion of the UV varnish for Black Glossy Chocolate Boxes on the problematic color box, we found that not only the UV varnish for Black Glossy Chocolate Boxes film but also a part of the ink layer was sticked off by the 3M transparent tape. In addition, we also found that after the normal printing process was completed and the metal ink was completely dry, a thin layer of metal powder was left on the finger when lightly swiped across the surface of the print. From this we judge: it may be that the binder in the metal ink is not enough. So we added some transparent inks to the metallic inks. After testing again, we found that the adhesion of the UV primer on the metallic inks was significantly improved, but it still failed to meet the customer's requirements. In this regard, we replaced the added transparent ink with quick-drying varnish, so that the adhesion problem of UV primer on metal ink was basically solved. However, the addition of quick-drying varnish dilutes the color of the metallic ink, resulting in a slight change in the color of the printed product, so it is necessary to add a little four-color ink to the metallic ink for redeployment. In addition, in the three processes after UV varnish for Black Glossy Chocolate Boxesing, mainly the water content of the color box will affect the abrasion resistance of UV varnish for Black Glossy Chocolate Boxes, so it needs to be controlled to a certain extent.

Program summary

Finally, the author summarizes the technical points of the abrasion resistance and adhesion of UV varnish for Black Glossy Chocolate Boxes on metal ink as follows.

(1) Production process route: plate making and paper cutting → ordinary printing → UV primer → UV finish.

(2) Use high abrasion resistance UV top oil and oily UV primer.

(3) Add 10% to 20% of quick-drying varnish to the metal ink (the specific ratio is based on the metal ink being completely dried, the finger is lightly scratched on the surface of the printed product, and there is basically no metal powder on the finger. The color is diluted and can be formulated by adding four-color inks). It should be emphasized that the UV primer must be applied after the metal ink is completely dry.

(4) Quick-drying varnishes all contain ink driers. If the metal ink is still difficult to dry after adding quick-drying varnishes, a drier with the same drying properties as white drying oil can be appropriately added (addition amount ≤ 3% ), do not add red drying oil, because red drying oil can only speed up the drying speed of the surface of the ink layer, but cannot speed up the drying speed of the inside of the ink layer.

(5) In the process after glazing, the water content of the color box must be controlled below 16%.

(6) The brands of various materials in the production process route should be fixed, and the various process parameters of ordinary printing, UV primer, and UV topcoat processes should be kept stable, and relevant records should be kept.

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